Purpose: This paper aims to contribute to the knowledge base on leading and facilitating the growth of school improvement networks by describing the activities and challenges faced by network leaders. Design/methodology/approach: A total of 19 co-leaders from 12 networks were interviewed using a semi-structured schedule about the growth of their network, key leadership processes, "tipping points", structural design and knowledge flow and transfer. Annual review documents were also analysed. Findings: Five leadership activities focused on facilitating networks were identified. These were: "courting" potential partners and developing proposals for networked activity; working for partner alignment and buy-in into network goals and plans; creating structured opportunities for teachers to work together; embedding networked activity through formalisation and harvesting the knowledge generated by practitioners; and refocusing network efforts. These activities present tensions around negotiating purpose, securing ownership of network activity, time, trust and the balance between quick wins and long term activities. Originality/value: Internationally, networks are emerging as an increasingly common organisational form as well as a method for professional development, school improvement and to better serve pupil need. This paper adds to the limited research on network leadership and addresses increased calls for the intentional development of these organisational structures.